1. Field of the Invention
The invention provides nucleotide sequences from Coryneform bacteria which code for the oxyR gene and a process for the fermentative preparation of amino acids, in particular L-lysine, using bacteria in which the oxyR gene is enhanced. The oxyR gene codes for the transcription regulator OxyR, which belongs to the LysR family.
2. Discussion of the Background
L-Amino acids, particularly L-lysine, are used in human medicine and in the pharmaceuticals industry, in the foodstuffs industry and, most particularly in animal nutrition.
It is known that amino acids are prepared by fermentation from strains of Coryneform bacteria, in particular Corynebacterium glutamicum. Because of their great importance, attempts are constantly being made to improve the preparation processes. Improvements to the process may concern measures relating to fermentation, for example, stirring and oxygen supply, or the composition of the nutrient media, such as, the sugar concentration during the fermentation, or the working up to the product form by, for example, ion exchange chromatography, or the intrinsic output properties of the microorganism itself
The output properties of these microorganisms are improved by employing methods of mutagenesis, selection, and mutant selection. These methods yield strains that produce amino acids, such as the lysine analogue S-(2-aminoethyl)-cysteine, and are resistant to antimetabolites or are auxotrophic for metabolites important for regulation. In this manner, L-lysine can be obtained from these strains.
For a number of years, methods of the recombinant DNA technology have also been used for improving L-amino acid-producing strains of Corynebacterium. However, there remains a critical need for improved methods of producing L-amino acids and thus for the provision of strains of bacteria producing higher amounts of L-amino acids. On a commercial or industrial scale even small improvements in the yield of L-amino acids, or the efficiency of their production, are economically significant. Prior to the present invention, it was not recognized that enhanced expression of the oxyR gene encoding the OxyR transcriptional regulator would improve L-amino acid yields.